public class prog {
    public static void main(final String[] args) {
        int sum = 15;
        java.util.Scanner scan = new java.util.Scanner(System.in);

        int n = scan.nextInt();
        if (n >= 0 && n <= Math.pow(10, 6)) {

            int sign;
            for (int i = 1; i <= n; i++) {

                if ((sum < 15 || sum - i < 16) ) {
                    sum += i;

                }else{
                    sum-=i;
                }

            }
        }
        System.out.println(sum);


    }
}